Magnetic spring resonators



May 31, 1966 T. R. @MEARA 3,254,310

MAGNETIC SPRING RESONATORS Filed Aug. 21, 1962 5 Sheets-Sheet 1 Z #5 f J4 5o 53 fi/ 2 wmf-defend Armi/Vis( May 31, 1966 T. R. OMEARA 3,254,310

MAGNETIC SPRING RESONATORS Filed Aug. 21, 1962 5 Sheets-Sheet 2 May 31 T. R. O'MEARA MAGNETIC SPRING RESONATORS May 31, 1966 T. R. @MEARA 3,254,310

MAGNETIC SPRING RESONTORS May 3l, 1966 T. R. OMEARA 3,254,310

MAGNETIC SPRING RESONATORS a man Var/155 1/ United States Patent O 3,254,310 MAGNETIC SPRING RESGNATORS Thomas R. OMeara, Malibu, Calif., assignorto Hughes Aircraft Company, a corporation of Delaware Filed Aug. 21, 1962, Ser. No. 218,306 6 Claims. (Cl. S30- 63) This invention relates to resonant systems and particularly to systems utilizing a vibrating magnetic mass responding to magnetic spring forces to provide or process electrical signals at selected resonant frequencies. f

In conventional mechanical resonant systems, spring or elastic mechanisms are a major source of damping which also impedes the desired long term oscillation. Also, mechanically resonant systems are only tunable by mechanical changes which are complicated and slowly effective. Further, mechanically resonant systems inherently have a low Q factor and are not readily coupled t electric input and output circuits. A resonating system that reduces the spring losses to very low values and provides electrical tuning would be highly useful for low frequencyoperation, for example.

It is .therefore an object of this invention to provide electro-mechanical resonating devices that utilize magnetic spring forces for controlling the oscillatory move-,

ments.

It is a further object of this invention to provide improved lowfrequency electro-mechanical oscillating devices that are electrically tunable.

It is a still further object of this invention to provide electro-magnetic oscillating devices that are adapted for coupling to electrical input and output circuits.

It is another object of this invention to provide an irnproved tunable bandpass amplifier for low frequency operation.

It is still another object of this invention to provide an improved low frequency parametric amplifier.

Briefly, in accordance with this invention, resonating magnetic systems are provided that operate in a repulsive mode in some arrangements and in an attractive mode in other arrangements. A resonating system, operating in the first and secondrepulsive mode includes magnetic structures for providing spring forces with each structure having a terminating pole adjacent to a gap. A Vibrating magnetic mass is arranged in the gap so that opposite magnetic poles are adjacent to each other. First and second windings are wound around the respective first and second terminating poles for developing a periodic variation of the forces in the gap and for sensing signals induced by the vibrating magnetic mass. A control winding may be coupled in the magnetic path between the magnetic structures to control the total magnetic spring forces and provide tuning of the resonant frequency of the vibrating magnetic mass. In an oscillator in accordance with this invention, an amplifier is coupled between the first and the second windingsfto maintain continued oscillation. A bandpass amplifier is also provided by coupling a source of signals to the first winding of a first device and by coupling the second winding thereof through an amplifier to the first winding of a similar device. AA parametric amplifier in accordance with this invention couples an input signal to the first and second windings and couples a source of alternating pumping signals to the control Winding. Also in accordance with this invention an angularly rotating arrangement is provided that operates in the attractive Inode.

The novel features of this invention, as well as the invention itself, both as to its organization and method of operation, will best be understood from the accompanying description taken in connection with the accompanying drawings, in which like characters refer to like parts, and in which:

FIG. 1 is a partially schematic drawing showing the basic electro-mechanical resonating system for operating in the magnetic repulsive mode in accordance with this invention;

FIG. 2 is a sectional view taken at line 2 2 of FIG. 1 to further explain the arrangement of the vibrating magnet; j

FIG. 3 is a drawing of a portion of FIG. 1 for explaining the sensing of signals from the mechanical movement of the vibratingmagnet;

FIG. 4 is a schematic diagram of the electrically tunable bandpass amplifier in accordance With this invention;

FIG. 5 is a plan view of another arrangement of a resonating system operating in the magnetic attractive mode in accordance with this invention;

FIG. 6 is a sectional view taken at line 6-6 of FIG. 5 for further explaining the arrangement thereof;

FIG. 7 is a partially schematic drawing of a low frequency parametric amplifier in accordance with this invention;

FIG. 8 is a partially schematic drawing of a resonating device in accordance with this invention utilizing two resonating magnetic masses;

FIG. 9 is a schematic diagram showing waveforms of displacement, current 'and voltage as a function of time for explaining the operation of the oscillator of FIG. 1;

FIG. 10 is a spectral diagram of frequency Versus voltage for explaining the tuning of the bandpass amplifier of FIG. 4; and

FIG. 11 is a schematic diagram showing waveforms of displacement, current and voltage as a function of time for further explaining the operation of the parametric amplifier of FIG. 7.

Referring first to the oscillator device of FIG. 1 in accordance with this invention, mounting structure 10 may be of a ferromagnetic material such as a soft ferrite material having a bottom portion 12 and side portions 14 and 16. First and second magnets 15 and 17 are positioned as extensions of the side portions 14 and 16 and have-respective north (N) and south (S) polarities arranged so that a closed magnetic path is provided through the structure 10. Soft iron extensions 20 and 22 are attached to the north and south pole faces 19 and 21 re-v spectively of the magnets 15.and 17. A gap 26 is provided between the extensions 20 and 22 of respective magnets 15 and 17 and includes a moving or vibrating magnetic mass or magnet 28 maintained against vertical and lateral movement by a thin spring 30 mounted to the bottom portion 12. The thin spring 30 is selected to provide a minimumspring force. The magnet 28 may have a north and south pole respectively positioned toward the north and south pole faces 19 and 21 of the fixed magnets 15 and 1.7 to operate in a repulsive mode. The spring 30 maintains the vibrating magnet 28 in stable equilibrium in the center of the gap 26 between the extensions 20 and 22. It is to be noted that in accordance with this invention, a pivot support such as a knife edge may be utilized instead of the thin spring 30 to completely eliminate any mechanical spring forces.

An exciting winding or coil 34 is wound around the extension 22 near the magnetic pole face 21 and a sense winding 36 is wound around the extension 20 near the pole face 19. The exciting winding 34 has ends 38 and 40 and the sense winding 36 has ends 44 and 46 with the ends 38 and 44 adjacent to the gap 26. The sense winding 36 has the ends 44 and 46 coupled through respective leads 48 and 50 to an amplifier 52, which for example may amplify signals without a phase shift. The exciting winding 34 has the ends 38 and 40 coupled to respective leads 53 and 54 which in turn are coupled through respec- Ptented May 31, 196e 3 tive leads 58 and 60 to the amplifier 52. The leads 58 and 60 are also coupled to output terminals 62 and 64 to which oscillating signals may be applied. The leads 48 and 58 may be coupled to a suitable point of reference potential such as ground.

The spring forces developed by the permanent magnets and 17 in response to the fields of the windings 34 for restoring the oscillating magnet 28 to a dotted position 73 are indicated by magnetic lines 66 and 68 and for restoring the magnet 28 to the position of a dotted box 69 by magnetic lines 70 and 72. It is to be noted that similar magnetic lines are present at the front and back sides of the magnet 28 but are not shown for convenience of illustration. To further control the spring forces for selecting a desired frequency of operation, a field control coil 74 is wound around thebottom portion 12 of the structure 10, having one end coupled to ground and the other end coupled through a lead 76 -to a source of D.C. (direct current) tuning current 80. The source 80 may include a resistor S4 coupled to ground at a center tap and coupled at opposite ends to the positive and negative terminals of a battery 86. A movable arm 88 is coupled to the lead 76 to provide a potentiometer arrangement so that potentials above and below ground may be applied to the lead 76 to either enhance or decrease the field intensity or flux density provided by the magnets 15 and 17. This field intensity is indicated by an arrow 90 in the return path of the structure 10. In response to a positive potential, for example, applied to the lead 76, a D.C. current flows through the coil 74 to develop an enhancing field indicated by arrows 93 and 94 so as to increase the magnetic flux density in the magnets 15 and 17 and in the gap 26 and to increase the resonant frequency of vibration of the magnet 28.

As may be seen in the section of FIG. 2, the thin spring 30 may be relatively narrow to provide a minimum spring force while preventing lateral movement. The thin spring 30 may be attached to the bottom section 12 of the magnet 10 by a connection 96 which may be a solder joint, for example. It is to be noted at this time that FIG. 3 shows the magnetic lines of force of lines 98, 100, 102 and 104 indicating the shifting magnetic fields perturbed as a result of mechanical positions of the moving magnet 28 for inducing signals in the sense coil 36.

Referring now to FIG. 4, the structure of the tunable bandpass amplifier in accordance with this invention will be explained. The bandpass amplifier may include first and second resonating or oscillating elements 108 and 110 with the element 108 including a soft ferromagnetic or ferrite structure 112 similar to that of FIG. 1 and including magnets 115 and 117 which may respectively have north and south pole faces 116 and 118 with soft ferromagnetic or ferrite extensions 119 and 121 attached thereto. A gap 120 is provided between the extensions 119 and 121. An oscillating or vibrating magnet 124 is mounted at the center of the gap 120 by a thin spring 126 having north and south poles respectively adjacent to the extensions 119 and 121 or the north and south poles of the respective magnets 115 and 117 to operate in a repulsive mode. An exciting winding or coil 130 is wound around the extension 119 near the magnetic pole face 116 and a sense winding 132 is wound around the extension 121 near the magnetic pole face 118. The exciting winding 130 has first and second ends 134 and 136 and the sense winding 132 has first and second ends 138 and 140, with the ends 134 and 138 being adjacent to the gap 120. To control the field strength of the magnets 115 and 117 by controlling the lines of ux in the return path of the structure 112, a control coil 142 is Wound around the bottom portion of the structure 112. The structure of the element 108 is similar to that shown in the section of FIG. 2 and will not be explained in further detail.

A source 144 of A.C. (alternating current) signals applies signals through leads 146 and 148 to respective ends 136 and 134 of the exciting coil 130 with thelead 146 being coupled to ground, for example. As the resonating magnet 124 oscillates in response to signals applied to the exciting coil and at a frequency determined by the stable field force as controlled by the coil 142, an alternating signal is induced in the sense coil 132 at the resonant frequency or within a narrow passband centered at the resonant frequency. The sense coil 132 has ends and 138 coupled through respective leads 150 and 152 to an amplifier 154 to provide an output from the first element 108. The amplifier 154 may be a noninverting amplifier, for example.

The second oscillating element 110 includes a soft ferrite structure 156 having magnets 157 and 159 attached thereto each with respective magnetic pole faces 158 and 160 of north and south polarities. Soft ferrite extensions 161 and 163 are permanently attached to respective pole faces 158 and 160 with a gap 162 therebetween. An oscillating or resonating magnet 166 is positioned during stable equilibrium in the center of the gap 162 and held by a thin spring 168. The resonating magnet 166 has north and south poles adjacent to respective extensions 161 and 163. For providing tuning of the resonant frequency of oscillation, a control coil 170 is wound around the Ibottom portion of the structure 156 to vary the stable magnetic field force at the gap 162. An exciting coil 174 is Wound around the extension 161 and a sense coil 176 is wound around the extension 163, with the coil 174 having end-s 178 and 180 and the sense coil 176 having ends 184 and 186. The ends 178 and 184 are adjacent to the `gap 162.

The exciting coil 174 is coupled through leads 18.8 and to the amplifier 154 to respond to the signal sensed in the oscillating element 108 and periodically vary the spring forces to provide improved narrow band filtering. The leads 150 and 188 may be coupled to ground. The sense coil 176 is coupled at opeposite ends to leads 196 and 198 which in turn may be coupled to output tenminals 200 and 202 to which is applied the signal at the selected pass-band frequency. The lead 196 may be coupled to ground.

For simultaneously tuning both of the resonating elements 108 and 110 to select a desired passband, the control coils 142 and 170 have one end coupled to ground and the opposite end coupled to a lead 206 `which in turn is coupled to a tuning circuit 208. A resistor 210 is provided in the tuning circuit 208 having a center tap coupled to ground and opposite ends coupled to a suitable source of potential such as battery 212. A movable arm 216 is coupled to the lead 206 to provide a potentiometer arrangement so that potentials above or below ground may be applied to the leaid 206. In response to the selected potential, current either ows in a direction through the control coils 142 and 170 to enhance or to diminish the magnetic field strength of the fixed magnets indicated by arrows 217 and 218 so that the stable magnetic spring Iforce varies.

Referring now to FIGS. 5 and 6, an oscillating arrangement in accordance with this invention operating in the attractive mode includes an angularly vibrating or oscillating magnet 230 mounted between structural elements 234 and 236 in FIG. 6 having recesses 238 and 240l to which bearings 142 and 144 are freely rotatable. The magnet 230 has respective north and south pole surfaces 231 and 233. Mounted onopposite sides of the rotating magnet 230 and parallel to the axis 242 thereof are magnets 246 and 248 having north and south fpoles as shown. Mounted -between the magnets 246 and 248 at opposite ends thereof are structures 250 and 252, which may be of soft :ferrite material, with the structure 250 having a first extension or magnetic pole 258 and a second extension or magnetic pole 260 projecting therefrom with a space 262 therebetween and shaped with a circular surface to confonm to the movement of the oscillating magnet 230 around the axis 242. In a similar manner, 4the structure 252 has first and second extensions or magnetic poles 264 and 266 having a space 270 therebetween. The magnetic poles 264 and 266 have circular shaped pole surfaces to conform to the movement of the rotating magnet 230 around the axis 242. The magnetic poles 258 and 260 have a south polarity and the magnetic poles 264 and 266 have a north polarity as determined by the magnetic paths :between the Ipoles of the magnets 246 and 248. The field strength at the poles 258- and 260 for-providing tuning is controlled by a first coil 276 Wound' around an extension 278 and by a second control coil 280 wound around an extension 282 of the structure 250. To apply alternating exciting signals, an exciting Winding 282 is wound laround the magnetic pole 258 and an exciting winding284 is wound around the magnetic pole 260 being coupled together at one end and wound in opposite directions from each other. The exciting winding 282 has first and second ends 288 and 290 and the exciting winding 284 has first and second ends 292 and 294 with the ends 288 and 292 lbeing adjacent to the north pole of the angularly vibrating magnet 230. y

In a similar manner, the magnetic pole 264 has a sense winding 296 Wound therearound and the magnetic pole 266 has a sense winding 380 Wound therearound, being coupled together at one end and wound in opposite directions Lfrom each other. The Winding 296 has first and second ends 384 and 306 and the win-ding 300 has first and second ends 308 and 310 with the ends 304 and 308 being adjacent -to the south pole of the angularly rotating magnet 230.

The field control coils 276 and 280 may have opposite ends coupled to leads 316 and 318 with Ithe lead 318 being coupled to ground, 4for example, and the lead 316 being coupled to a tuning .circuit similar to the' circuit 208 of FIG. 4 when the arrangement of FIG. 5 is utilized in a bandpass amplifier for example. The exciting coils 282 and 284 may be coupled to leads 322 and 324 with the lead 322 being coupled to ground and the lead 324 being coupled to the source of A.C. signals 144 of FIG. 4. The sense coils 296 and 300 are coupled to leads 328 and 330 with the lead 328 being coupled to ground and the lead 330 :being coupled to the amplifier 154 of FIG. 4. Also, a similar oscillating element may be utilized in place of the oscillating element 110 in FIG. 4 by suitably coupling the leads 324 and 322, at the amplifier 154 and the leads 330 and 328 to the output terminals 200 and 202. -As will be explained subsequently, the arrangement of-FIG. 5 operates in the attractive mode with the exciting windings changing polarity to attract the pole surface 231 to the magnetic pole 260 when the end 292 of the winding 284 has a south polarity and to attract the pole surface 231 to the magnetic pole 258 when the end 288 of the Winding 282 has a south polarity. An alternating signal in phase with the signal applied to the lead 324 is induced in the sense coils 296 and 300 by the angular vibration or rotation through an angle df the magnet 230. l

Referring now to FIG. 7, the general structural arrangement of the parametric amplifier operating in the repulsive mode in accordance with this invention will be explained. The resonating element includes a structural frame 342 of a ferromagnetic material such as a soft ferrite material having a first magnet 344 positioned at one end and a second magnet 346 positioned at the other end with .a north pole face 345 of the magnet 344 and a south pole face 347 of the magnet 346 being positionedtoward a gap 348. An oscillating or resonating magnet 350 is positioned during stable equilibrium at the center of the gap 348 by a thin spring 352 mounted to the frame 342 with the north pole of the magnet 350 being positioned toward the north pole of the magnet 344 .and the south pole of the magnet 350 being positioned toward the south pole of the magnet 346. Soft ferrite extensions or structures 349 and 351 are respectively mounted on the pole faces 345 and 347 of the magnets-344 and 346 with the gap 348 being therebetween. A first winding 358 is-wound around the extension l349 and a second winding 360 is wound around the extension 351, being wound in the same direction, for example. The coil 358 may have a rfi-rst end '364 and a second end 366 and the second coil 360 may have a first end 368 and a second end 370. The ends 364 and 368 Imay be coupled to ground and the ends 366 and 370 may be coupled to a lead 374. To provide the parametric driving force, a parametric winding k376 is wound around the structure 342 to control the total intensity of the magnetic field developed in the gap 348.

A source of input signals to be amplified is provided by a source 381 which may include Van oscillator 380 operating at an input frequency wo and coupled through a lead 382 to a phase shifter circuit 384, which in turn is coupled -to a lead 386. The input signal is applied from the -lead 386 to the lead 374 and af-ter amplification .to a load 390 to ground. The pumping signal which is applied to the parametric coil 376 may be provided by a harmonic generator 394 including a rectifying diode 396 having an anode coupled through a lead 398 to the oscillator 380. The cathode of the diode 396 may be coupled to a lead 400 which in Iturn is coupled `through Ia resistor 402 to ground. The rectified signal on the lead 400 is then applied to a @filter 404 -which is tuned to twice the frequency wo of the oscillator 380. Thus, a signal at the pumping frequency is applied from the :filter 404 through a lead 408 to a current generator 410; The pumping signal of the current generator 410 is then applied through a lead 412 to a first end of the parametric coil 376, the Aother end of the parametric coil being coupled to ground.

It is to be noted that the arrangement of the harmonic generator 394 is shown to illustrate one method of maintaining a phase lock between the input signal and the pumping signal, although other arrangements may be utilized in accordance with this invention. Also, it is to be noted that the phase shifter 384 is provided to correct any undesired phase shift developed in the filter 404 because of phase shift variations from the zero. phase shift characteristics of an ideal filter.

As will be explained subsequently, the A.C. pumping signal applied to thev lead 412 -develops magnetic fields indicated by lines 418 and 420 for increasing the intensity of the field at the gap 348 in the required phase relation lwith the input signal applied to the lead 886 from the source 381 so as Ito provide amplification of the input signal on the lead 386. The resonating magnet 350 responds to a field of force indicated by lines 322 and 323 in a first position and by `lines 326 and 328 in va sec ond position in the gap 348.

Referring now `to FIG. 8, which is an .arrangement in accordance with the invention that is relatively unsusceptible to shock excitation includes first and second oscillating or resonating magnets 436 and 438, each mounted by respective thin springs 440 `and -442 on a fixed frame such as 444 of a relatively soft ferromagnetic or ferrite material. At eachend of the frame 444 are first and second magnets 448 and 450 with the magnet 448 having a south pole face 449 and ythe magnet 450 having a south pole face 451, being respectively adjacent to soft ferrite poles or extensions 453 and 455. A first winding 456 is wound around the extension 453 and a second winding 458 is wound around the extension 455. The first winding 456 has first and second ends 460 and 462 'with Ithe end 460 being adjacent to the gap 454, and the second winding 4518 has first and second ends 464 and 466 with lthe end 464 being adjacent to the gap 4514. Sensing is performed by -a soft ferrite structure 457 mounted by a suitable Ifixed member 459 at a position adjacent to the oscillating magnet-s 436 and 438 and substantially at a center position of the gap 454. The 'fixed members 459 may be attached to other Ifixed structure (not shown). A sense winding 461 is wound around the structure `457 substantially at right angles to the direction of movement of the magnets 436 and 438. First and second ends of the coil 461 are coupled to leads 483 and 485 which in turn are coupled to terminals 463 and 465.

To utilize the repulsive system of FIG. 8 in the bandpass amplifier of FIG. 4, for example, the end 462 of the coil 456 is coupled through a lead 468 to a lead 479 which -in turn is coupled to the end 464 of the coil 458 and the end 460 is coupled through a lead 472 to a lead 473 which in turn is coupled to the end 466 of the coil `458. The leads 473 and 479 are coupled to respective terminals r467 and 469. The terminals 467 and 469 may be coupled to the source of A C. signals v144 of FIG. 4 and the .terminals 463 and 465 are coupled to the leads l150 and 152 and to the amplifier y154. A similar arrangement may be utilized between the amplifier 154 and the output terminals 202 and 280. The oscillating movement of the magnets 436 and 438 is provided by the fields of lthe windings 456 and 458 varying in configuration and .the `repulsion developed between like magnetic poles so that the oscillating magnets alternately move together and apart. The exciting fields developed by the windings 456 and 458 are shown for one condition by lines 489 and 491 and in another condition by lines 493 and 495. The magnetic fields of the resonating magnets 436 and 438 that-induce the output signal in the winding 461 are indicated by Ilines 497 and 499. It is to be noted that a control coil (not shown) for tuning may be utilized but because of the like poles of the fixed magnets is less effective than in the other arrangements `in accordance with this invention. The structure of the resonating element of FIG. 8 is similar to that shown in the cross section of FIG. 3 and will not be explained in further de, tail.

Now that the general arrangement of the resonating devices in accordance with this invention have been explained, the operation of the oscillator of FIG. 1 will be explained by also referring to FIGS. 3 and 9. A waveform 494 shows the displacement of the oscillating magnet 28 through the center position to a position No. l between timesV to to t1 as indicated by the dotted magnet 73. The system may initially start oscillation in response to a disturbing or impacting force applied to the magnet 28. A restoring force or spring force proportional to the displacement then maintains the magnet 28 oscillating at a resonant frequency as determined by the mass thereof and by the spring force.

At times t and t2 when the magnet 28 is at the center position the only force applied to the magnet 28 is from shifting fields which result from the driving current excitation. At times t1 and t3 which are the maximum displacement times, the only force applied to the magnet 28 is from the shifting fields perturbed as a result of mechanical position, that is, the repelling force between opposite magnetic poles.

At time to, the magnet 28 is in the center position and the positive exciting current of a waveform 496 is applied through the lead 54 to the exciting winding 34 as the magnet 28 moves through the center position from position No. 2. The magnetic field in the winding 34 is developed therein to enhance or augment the magnetic field indicated by the arrow 90 so that the lines of flux pass from the magnet 15 to the magnet 17 as shown by the lines 66 and 68. Thus, there is a crowding of magnetic lines of force lat the face of the extension 22 to provide a restoring force to oppose the south pole of the magnet 28 so that the oscillating magnet 28 is moved to the position No. 1 as shown by the dotted magnet 73.

As the magnet 28 moves to the position No. l, the voltage induced'in the sense coil 36 as shown by a waveform 498 changes polarity. In position No. 1 at time t1, the component of the magnetic field resulting from the mechanical position vof the magnet 28 disturbs the magnetic field to generally appear as indicated by lines 98 and 100 of FIG. 3. Because of the field of the magnet 28 the lines of ux indicated by the lines 98 and 180 are generally directed to the end 46 of the coil 36, thus decreasing the density of the lines of force at the position No. 1. This change of position of the lines of flux induces the output voltage of the waveform 498 in the coil 36 which is applied to the amplifier 52. The lines 98 and are shown at the extreme position with the maximum displacement of the lines of iiux, but this change of the lines is continuous as the magnet 28 moves to the position No. 1.

At position No. 1 at time t1, the exciting current is zero and the restoring force results from the repulsion of the north poles of the magnets 15 and 28. As the current of the waveform 496 decreases between times t1 and t2, the field of the coil 34 decreases and the magnet 28 is forced to the center position with increased spring force resulting from the exciting current and decreased force resulting from the position. At time t2 the lines of ux resulting from the exciting current inhibiting the magnetic force at the extension 22 have a position shown by lines 70 and 72 and essentially pass between the pole face 19 and the pole face 21. Thus, at time t2 the maximum spring force from the exciting current forces the magnet 28 toward position No. 2. At time t2, the field induced in the sense winding 36 by the changing lines of flux in the gap 26 develops a maximum sensed signal as shown by the waveform 498. At time t3, the magnet 28 is at the position No. 2 with the exciting force decreased to zero and the repelling force resulting from the position of the magnet 28 increased to a maximum. At time t3 the flux component resulting from the position of the magnet 28 is indicated by the lines 102 and 104 of FIG. 3. Thus at this extreme condition the output voltage of the waveform 498 passes through zero voltage.

Between times t3 and t4 the enhancing field of the coil 34 increases to a maximum and the magnet 28 returns to the center position at time t4. The output signal of the waveform 498 is continually induced in the winding 36 by the change of geometry or spacial positions of the magnetic field in the gap 26 as a result of the movement of the magnet 28, which induced signal controls the exciting Winding 34. This operation continues in a similar manner at time t5 and during continued oscillation and will not be discussed in further detail. Thus, the magnetic spring forces overcome the momentum of the moving magnet 28 at positions No. l and 2. The displacement energy represented by the magnetic springs and the energy of motion alternately change to provide the continued oscillation.

The magnetic spring force developed at the gap 26 thus control the oscillation of the magnet 28 at a resonant frequency to provide a continuously operating oscillator with any losses such as air friction or eddy current losses being supplied by the amplifier 5K2. As is well known, the angular resonant frequency of vibration may `be expressed as w0=\/K/M where M is the mass of the vibrating magnet and K is the rate of change of the magnetic force with distance. Because the spring forces determine the resonant frequency of vibration and the magnetic lines of flux have a continuous path through the structure 10 as shown by the arrow 90, the coil 74 controls the total density or strength of the magnetic field at the gap 26 to provide tuning of the resonant frequency of the resonating magnet 28.

The strength of the magnetic field as controlled by the coil 74 for a selected resonant frequency is always the same at a selected position of the magnet 28. When the arm 88 is moved toward the positive potential of the battery 86, current flows from the lead 76 to the coil 74 to ground. Thus, a magnetic field is developed as indicated by lines 91 and 93 to enhance or increase the density of the lines of flux at the gap 26 which increases the total spring forces or the spring force at any selected position of the magnet 28 and increases the resonant frequency of oscillation of the magnet 28. As a result, the frequency of the sensed signal of the waveform 498 and the signal of the Waveform 496 is increased and applied to the output terminals 62 and 64 as the magnet 28 vibrates between positions No. 1 and No. 2 at an increased resonant frequency.

When the arm 88 is at the groundtap of the resistor 84, a field is not developed in the control coil 74 and the frequency of oscillation is determined by the permanent magnetic field intensity of the magnets 15 and 17. As the arm 88 is moved toward the negative terminal of the battery 86, current Hows from ground through the coil 74 to the lead 76 developing a magnetic field of an opposite polarity from the arrows 91 and 93. As a resuit, the lines of flux at the gap 26 are decreased at each position of the magnet 28 to decrease the magnetic spring force which in turn decreases the resonant frequency of oscillation and the frequency of the sensed signal of the waveform 498. Therefore, an electrically tunable oscillator is provided.

The gravitational forces may be considered when operating the resonant devices of this invention within the gravitational fields of the earth. Thus, the magnetic forces are selected with an order of magnitude of three to ten times the forces of gravity so as to have a minimum effect on the reliability of operation. The systems such as the oscillator of FIG. 1 are preferably arranged so that the gravitational force will be applied symmetrically to the moving magnetic mass during a complete cycle.

This oscillator of FIG. 1 has a relatively large Q factor which may be defined as the ratio of stored energy to dissipated energy per cycle of oscillation. The spring forces of the oscillator are developed from magnetic fields which themselves have relatively small internal dissipation. The Q factor is only decreased by radiation and heat losses such as air friction. It is to Abe noted that the high Q factor of the oscillator of FIG. 1 provides highly stable operation. The soft ferrites utilized in the arrangements in accordance with this invention to provide paths for the magnetic lines of flux have a small reluctance so as to provide very small eddy current losses. However, other materials having similar characteristics may be utilized in accordance with the invention for directing magnetic fields. Any losses in the system are overcome by the energy supplied from the amplifier 52 to provide continued oscillation.

Referring now to the bandpass amplifier of FIG. 4, the resonant vibration of the magnetic mass is similar to that of FIG. 1. After the magnet 124 is initially in oscillation resulting for example from noise developed by initially applying signals to the system, a signal at the resonant frequency or within the passband is applied from the source 144 through the coil 130 and may be at maximum positive value at time t of FIG. 9 as shown by the current waveform 496 when the magnet 124 is in the center position. The coil 130 thus develops a field to enhance the magnetic field and the lines of flux resulting from the exciting current pass from the face of the extension 134 to the end 140 of the coil 132. Thus, the increase of force at the end of the extension 134 c auses the magnet 124 to move from the center position to the position of adotted box 133 at time t1. The displacement of the magnet 124 is similar to the waveform 494 with the position of the dotted box 133 being at position No. 1. At time t1, the restoring force is supplied entirely by the opposite poles between the magnet 124 and the extension 138 resulting from the position of the magnet 124 and the induced signal results from the geometrical change of the lines of ux as discussed relative to FIG. 3.

The signal induced in the coil 132 which is similar to the signal of the waveform 498 is applied through the amplifier 154 where any energy losses are supplied and to the` exciting winding 174. The oscillating magnet 166 responds in a similar manner as the magnet 124 with the output resonant signal being similar to the waveform 498. It is to be noted that two stages are shown for the bandpass amplifier but additional stages may be utilized for improved narrow band filtering as is well known in the art.

In a similar manner, between times t1 and t2 as the magnet 124 moves away from the position 133, the polarity of the field developed in the coil 130 is reversed to develop magnetic lines of flux between the end 136 of the coil 130 and the end 138 of the coil 118. These lines of flux which provide a maximum restoring force when the magnet 124 is in the center position move the oscillating magnet 124 to a position indicated by the dotted box 135 at the time t3. This position corresponds to position No. 2 0f the waveform 494 of FIG. 8. In a similar manner, a signal similar to the waveform 498 is sensed by the coil 132 as a result of the change of the magnetic field by the displaced position of the magnet 124 and applied through the amplifier 154 to excite the winding 174. The oscillating magnet 166 thus resonates in synchronism with the magnet 124 to apply the signal similar to the waveform498 to the output terminals 202 and 200. This operation continues between times t3 and t5 with the magnetic polarity of the field developed by the coils 130 and 174 reversing at times t3 and t5.

Tuningof the resonant frequency of the resonating eley ments 108 and 110 is provided by the coils 142 and 170 to control the magnetic density and the restoring spring forces as discussed relative to FIG. 1. By moving the arm 216 of the tuning circuit 208, the field strength developed by the coils 142 and 170 are both varied to change the resonant frequency of oscillation of both the oscillating `magnets 124 and 166 simultaneously. The tuning operation varies the total field between the magnets and 117 and between the magnets 157 and 159 or varies the field intensity at any selected position of the oscillating magnets 124 and 166. v

Referring now to the spectral diagram of FIG. 10, when the arm 216 is at the ground tap of the resistor 210, a passband 500 is provided with the resonant frequency shownv by a spectral line 502. If another signal within the passband such as shown by a spectral line 504 is applied to the lead 148 the amplitude is attenuated by the decreased distance of movement of the magnets 124 and 166. Also, as is well known in the art, if several signals such as shown by the spectral lines 502 and 504 are simultaneously applied to the lead 148, the distance of movement and the frequency is a composite component thereof. When the arm 16 is moved to a position between the ground tap and the positive terminal of the battery 212 along the resistor 210, the field strength is enhanced and the resonant frequency as well as the passband moves to positions such as shown by passbands 506 and 508. Also, when the arm 216 is moved along the resistor 210 to a position between the ground tap and the negative terminal of the battery 212, the magnetic field of the oscillating elements 108 and 110 are decreased. Thus, the magnetic spring force is decreased and the resonant frequency and passband moves to a lower frequency such as shown by passbands 512 and 514. It is to be noted that in the arrangements having thel configuration of FIGS. 1 and 4, substantially linear movement of the resonating element is provided because of the relatively large length of the thin springs.

Similar to the oscillator of FIG. 1, the bandpass amplifier of FIG. 4 has a high Q factor because of the relatively small losses of the magnetic system. It is to be noted that in the arrangements in accordance with this invention, coupling from an electrical source into and out of the mechanical elements is greatly simplified.

Referring now to FIG. 5, an arrangement of the resonating element operating in an attractive mode in accorci-A ance with this invention will be explained. The exciting windings 282 and 284 respond to a current signal similar to the waveform 496 to provide a maximum attraction i 1 of the magnet 230 to the pole 260 at the time l of FIG. 9 by inhibiting the south polarity at the pole 258 and enhancing the south polarity at the pole 260. In a similar manner, a Voltage similar to the waveform 498 is induced in the sense coils 296 and 300, being in phase with the exciting signal similar to the waveform 496. At time t1 the magnet 230 changes direction of rotation as the attractive force is reversed. At time t2 as the magnet 230 passes through the center position or horizontal position of FIG. 5 and in response to the negative going signal of the waveform 496, the polarity of the field developed by the coils 282 and 284 is such that the south pole is enhanced a maximum amount at the magnetic pole 258 and is inhibited a maximum amount at the pole 260.

As a result of this attractive force, the magnet 230 is angularly rotated to the position adjacent to the pole 258, being at the maximum angle at time t3. This operation continues in a similar manner and will not be explained in further detail. The angular displacement of the magnet 230 around the axis 242 varies sinusoidally similar to the waveform 494. As the magnet 230 rotates a few degrees around the position shown, the output signal similar to the waveform 498 is induced in the coils 296 and 300.

Tuning is provided by the control coils 276 and 280 similar to the arrangement of FIG. 4. It is to be noted that if the oscillating element of FIG. 5 operating in the attractive mode is to be utilized in the bandpass amplifier of FIG. 4, similar arrangements are coupled to the source of A.C.. signals 144, to the amplifier 154, to the output terminals 200 and 202, and to the tuning circuit 208. An

advantage of the systemof FIG. 5 is that if the magnetic forces are selected to exceed the weight of the magnet 230, gravitational forces exerted on the pivots at the recesses 238 and 240 are substantially eliminated.

Referring now to FIG. 7, the operation of the parametric amplifier in accordance with this invention will be explained in further detail. It is to be noted that although D.C. field control is illustrated in the oscillator and the bandpass amplifier by providing A.C. control of the field, all the elements of a parametric amplifier are present. Thus, in the parametric amplifier the field excitation is operated at twice the resonant frequency and the variable magnetic spring constant K is analogous to the variable elasticity of an electrically resonant parametric system. Referring also to the waveforms of FIG. 11, a waveform 520 shows the displacement of the oscillating magnet 350 between times to and t5. The input current signal of a waveform 524 is applied to the lead 386 and to both of the windings 358 and 360. Simultaneously, a current signal of a waveform 528 at the pumping frequency which is twice the resonant frequency is applied to the lead 412 andv through the parametric coil 376.

At time to, the input signal of the waveform 524 is at a maximum positive value and the magnet 350 is in the center position. A maximum field is developed in the coils 358 and 36) to oppose the field of the magnet 344 and to enhance or augment the field of the magnet 346. Thus, the magnetic lines of force in the gap 348 have the shape shown by the lines 322 and 323. As a result, the magnet i) is forced to the position shown by a dotted box 532 at time t1. As the amplitude of the input signal of the waveform 524 decreases from its peak at time to, and the magnet 350 moves toward position of the box 532'the enhancing field of the coil 368 and the inhibiting field of the coil 358 gradually decrease until at time t1 only the force resulting from position remains. Thus, at time t1 the oscillating magnet 350 changes direction of movement as'a result of the adjacent opposite poles of the extension 349 and the magnet 350. Between times t1 and t2, the current direction through the coils 358 and 360 is reversed so that the magnetic field of the magnet 344 is enhanced an increasing amount while the magnetic field of the magnet 346 is inhibited a decreased'amount to form magnetic spring force indicated by lines 326 and 328 indicated when the magnet 350 is at the center position at time t2. As a result, the oscillating magnet 350 moves to a position shown by a dotted box 536 at the time t3. Between times t3 and t4 the field of the coils 358 and 360 decreases with the magnet 350 moving toward the center position with an increasing force from the exciting current and a decreasing force resulting from the position of the magnet 350. At time t4 the magnet 350 is returned to its center position as indicated by the displacement curve of the waveform 520 and Aagain restored to the position of the box 532 at time t5.

During this operation, signals of a waveform 540 are induced in the coils 358 and 360 resulting from magnetic components similar to the lines 98 and 168 and lines 102 and 104 of FIG. 3 indicating the fields at the extreme positions on each side of the center position. The induced voltage signal is applied to the load resistor 390 as is well known in the parametric amplifier art.

To explain the operation of the pumping signal to transfer energy to the load by increasing the intensity of the magnetic spring force, the current of the waveform 528 increases to a peak at time t1 which coincides with the peak of the displacement of the waveform 520 and zero exciting current of the waveform 524. Thus, at time t1 the maximum current through the parametric coil 376 causes the field to be a maximum, thus increasing the density of magnetic lines of force passing through the gap 348. Therefore, the field in the gap 348 is increased to a maximum at time t1 so that more lines of flux asindicated in FIG. 3 are cut in the coil 358 to amplify the output voltage of the waveform 548.

In a similar manner at time t3, the increased current of the waveforms 528 when the magnet 350 is at the position 536, causes increased lines of fiux to be cut by the winding 360 so as .to amplify the signals of the waveform 540. Thus, parametric amplification is provided and the input signal of the waveform 524 applied to the lead 374 is effectively amplified to provide the load voltage of the waveform 548 at the load resistor 390. The general theory of parametric amplification is well known in the parametric amplifier art and will not be explained in further detail.

A voltage signal on the lead 412 (not shown) to develop the current signal of the waveform 540 lags the current signal of the waveform 524 with the phase shift principally provided by the inductance of the parametric coil 376 as is well known in the art. The harmonic generator 394 is shown as an illustration of an arrangement to provide the pumping signal by rectification in the diode 396 and by filtering in a tuned circuit. The phase shifter 384 is shown to provide any phase correction required because the characteristics of the tuned filter 484 may vary from those of an ideal filter. It is to be noted that the principles of this invention are not to be limited to the particular arrangement of applying the input signal or of developing the signal at the pumping frequency, as many other conventional arrangements may be utilized.

Another arrangement in accordance with this invention as shown in FIG. 8 operates with two magnets resonating in the repulsive mode to provide a minimum susceptibility to shock vih-ration. The oscillating magnets 436 and 438 v are instantaneously maintained at positions resulting from a balance of the forces between the like magnetic poles and the spring forces between the fixed magnets 448 and 450 indicated for one condition by the lines 489 and 491. The oscillating magnets 436 and 438 simultaneously move away from each other or toward each other in response to an oscillating current signal at or near the resonant frequency similar to that of the waveform 496 of FIG. 9. As the magnets 436 and 438 move, the magnetic fieldsresulting from the position induce an output in the coil 461 similar to the waveform 498. Thus, the magnets 436 and 438 both move from the position shown (center position) toward each other indicated as position No. 1 between times t and t1 as the fields of the winding 456 and 458 inhibit in decreasing amounts the fields of the magnets 448 and 450. This force is indicated at the center position or time to by lines 493 and 495. Between times t1 and t2 the repulsive forces resulting from position of the moving magnet decrease from a maximum and the field of the windings 456 and 458 increases or enhances the fields thereat so that the magnets 436 and 438 are forced away from each other to the center position at time f2. Between times t2 and t3 the enhancing fields of the coils 456 and 458 decrease until the magnets 436 and 438 are at position No. 2. At time t2 the field resulting from the exciting current is shown by lines 489 and 491. At time t3 the exciting current is zero and the only restoring force results from the repulsion of opposite'poles of the magnets. In the arrangement of FIG. 8, both coils 456 and 458 inhibit or enhance the magnetic fields simultaneously so as to develop the spacial or geometrical fields required for the magnetic spring forces. The fields of the magnets 436 and 438 indicated by lines 497 and 499 induce a signal similar to the waveform 498 in the sense coil 461 as the magnets resonate.

The geometrical arrangement of the lines of force between the north pole of the magnet 448 and the south pole Vof the magnet 450 both alternately change at each half cycle so that the oscillating magnets 436 and 438 continuously .move in synchronism either toward each other or away from each other. The voltage similar to the wave-l form 498 induced in the coil 461 by the fields of the magnets 436 and 438 is applied to the output terminals 463 and 465 andmay be within a passband centered at the Vresonant frequency when the arrangement of FIG. 8 is utilized on a biandpass amplifier as discussed relative to FIG. 4. It is to be noted that a field control coil for tuning (not shown) similarto that shown in FIG. 5 may also be utilized in the arrangement of FIG. 8 in accordance with the principles of this invention. VIn the system of FIG. 8 in response to a shock force such as one applied to the structure 444, the magnets 436 and 438 may jointly oscillate as well as the resonating movement discussed above. However, because the fields of the lines 489 and 491 both induce the output signal in the winding 461, the output signal is not changedor noise is not added thereto.

Another advantage of the system of FIG. 8 is that because the sense winding 461 is parallel to the direction of movement of the fields of the magnets 436 and 438, the system operates without transformer type coupling between the sense coil and the resonating arrangement.

Thus, there has been described electro-mechanical resonating systems in which the geometrical configuration or spacial arrangement of the magnetic fields is controlled by an alternating signal to provide a varying magnetic spring force. The moving magnetic mass oscillates at a resonant frequency in response to the alternating signal at or-near the resonant frequency. The total magnetic force may be varied by either D.C. control or A.C. control. The principles in accordance with this invention provide improved oscillators, tunable oscillators, narrow band filters, and parametric amplifiers. The arrangem-ents in accordance with this invention provide improved electrical coupling thereto and develop a relatively high Q factor. Thus, improved resonant oscillating devices are provided for operation in the relatively low frequency ranges such as within the range of l to 1000 cycles per second, for example.

What is claimed is:

1. A resonating device comprising first and second fixed magnetic means Ipositioned with a gap therebetween,

said first and second magnetic means having opposite magnetic poles adjacent to said gap to develop a magnetic field in said gap; a movable magnet positioned in said gap and having a selected mass, said'movable magnet having first and second magnetic poles adjacent like poles of said fixed magnetic means; means to provide an essentially closed magnetic path return between said first and second fixed magnetic means; first and second coils 2. A resonating device comprising first and second per-` manent magnetic means positioned to form a gap therebetween with opposite magnetic poles adjacent to said gap; a ferromagnetic structure positioned between said first and second magnetic means at the magnetic poles opposite to those adjacent to said gap for providing a return magnetic path therebetween, said first and second Y magnetic means developing a magnetic field in said gap;

a magnetic mass mounted in said gap and movable between said first and second magnetic means, said magnetic mass having poles adjacent to like poles of said first and second magnetic means; first and second windings respectively wound around said first and second magnetic means substantially adjacent to said gap; a source of alternating signals coupled to said first winding for alternately enhancing and inhibiting said magnetic field during alternate half cycles to vary the spacial arrangement of said field for developing magnetic restoring forces which in combination with the repulsive forces between like magnetic poles of said magnetic mass and said first and second permanent magnetic means maintains said magnetic mass oscillating in said gap at a resonant frequency; means coupled to said second winding for responding to the signal developed thereat; and control means positioned around said structure for varying the magnetic field developed in said gap by said permanent magnetic means so as to vary the resonant frequency of oscillation of said magnetic mass.

3. A resonating device comprising first and second permanent magnetic means positioned to form a gap therebetween with opposite magnetic poles adjacent to said gap; ferromagnetic means to provide a relatively low reluctance magnetic path between said first and second permanent magnetic means and mounted at magnetic `poles thereof opposite said gap; a movable magnetic said first winding to develop magnetic spring forces .in

saidgap for maintaining said movable magnetic mass oscillating in said path at a resonant frequency determined by the mass of said magnetic mass and by the force of said spring forces, said means responding to alternating signals induced in said second winding; a control winding magnetically coupled to said ferromagnetic means; and a source of control current coupled to said control winding for varying the strength of said spring forces to vary the intensity of the magnetic field at said gap and provide selection of a desired resonant frequency of oscillation of said magnetic mass.

4. A resonating device comprising first and second permanent magnetic means positioned to form a gap therebetween with opposite magnetic poles adjacent to said gap to form a magnetic field therein; ferromagnetic means to provide a magnetic path between said first and second permanent magnetic means and mounted at the magnetic poles opposite those adjacent to said gap; a movable magnetic mass positioned in said gap with like magnetic poles adjacent those of said first and second magnetic means; means mounted to said magnetic mass for substantially restraining the movement thereof to a -path between said first and second magnetic means; winding means magnetically coupled to the magnetic field in said gap; means coupled to said winding means for applying alternating signals to develop magnetic spring forces in said gap for maintaining said movable magnetic mass oscillating in said path at a resonant frequency determined by the .mass of said magnetic mass and by the force of said spring forces; a control winding magnetically coupled to said ferromagnetic means; and a source of control current cou-pled to said control winding for varying the strength of said magnetic spring forces at said gap.

5. A resonating device comprising first and second permanent magnetic means positioned with a gap therebetween and with opposite magnetic poles adjacent to said gap, said first and second magnetic means developing a magnetic field in said gap; first and second movable magnets positioned in said gap with like magnetic poles adjacent to each other and to the poles of said first and second magnetic means at said gap; means mounted to said first and second movable magnets for restraining movement thereof to a direction between said first and second magnetic means; first and second coils magnetically coupled to said respective first and second magnetic means adjacent to said gap; a source of alternating signals coupled to said first and second coils for periodically enhancing the magnetic fields and inhibiting the magnetic fields at both coils to develop a spring force to maintain said first and second movable magnets oscillating at a resonant frequency; and sensing means positioned adjacent to said first and second movable magnets to sense an output signal at said resonant frequency from the movement of the magnetic fields of said first and second movable magnets.

6. A resonating device comprising, first and second magnets positioned substantially parallel to each other with like poles adjacent to each other; first and second ferromagnetic structures respectively positioned between the like poles of said first and second magnets and each having first and second extensions with the extensions of the first and second structures directed toward each other; a rotatable magnet positioned between said first and second ferromagnetic structures so as to rotate on an axis at right angles to the first and second extensions of said first and second structures; first and second exciting windings wound around the respective first ferromagnetic and second extensions of said first structures and coupled together at one end; first and second sensing windings wound around the respective first and second extensions of said second ferromagnetic structure and coupled together at one end; and first and second controlwindings wound around said first ferromagnetic structure and coupled together at one end for controlling the field applied to said rotatable magnet, said first and second exciting windings responding to an alternating signal coupled thereto at a predetermined resonant frequency to alternately and oppositely inhibit and enhance the magnetic field thereat to alternately attract the rotatable magnet to the first and second extensions thereof so that said rotating magnet cnanges angular position at said resonant frequency, said rotatable magnet inducing a signal in said first and second sensing coils, said control winding responding to a selected current to control the magnetic field force and vary the resonant frequency.

References Cited by the Examiner UNITED STATES PATENTS 1,702,568 2/ 1929 Marrison 333-71 2,147,492 2/1939 Mead 331-156 2,710,314 6/1955 Tongue et al. 330-154 X 2,948,819 8/1960 Goto.

3,099,801 7/1963 Jorgensen S30-4.5 X

ROY LAKE, Primary Examiner.

NATHAN KAUF MAN, Examiner. 

1. A RESONATING DEIVCE COMPRISING FIRST AND SECOND FIXED MAGNETIC MEANS POSITIONED WITH A GAP THEREBETWEEN, SAID FIRST AND SECOND MAGNETIC MEANS HAVING OPPOSITE MAGNETIC POLES ADJACENT O SAID GAP TO DEVELOP A MAGNETIC FIELD IN SAID GAP; A MOVABLE MAGNET POSITIONED IN SAID GAP AND HAVING A SELECTED MASS, SAID MOVABLE MAGNET HAVING FIRST AND SECOND MAGNETIC POLES ADJACENT LIKE POLES OF SAID FIXED MAGNETIC MEANS; MEANS TO PROVIDE AN ESSENTIALLY CLOSED MAGNETIC PATH RETURN BETWEEN SAID FIRST AND SECOND FIXED MAGNETIC MEANS; FIRST AND SECOND COILS MAGNETICALLY COUPLED TO SAID RESPECTIVE FIRST AND SECOND 